function  s() {
    //0,页面初次渲染的时候，小计会是每个商品的单价*数量
    let  tr=document.querySelectorAll("#table tr");
//总价
    let all=document.querySelector("#all");
    let alla= 0;

    for(let i=0;i<tr.length;i++){
        //单价
        //console.log(tr[i].children[2].children[0].innerHTML)
        //数量
        //console.log(tr[i].children[3].children[0].value)
        //小计
        //console.log(tr[i].children[4].children[0])
        var price=tr[i].children[2].children[0].innerHTML;
        var num =tr[i].children[3].children[0].value;
        var total=tr[i].children[4].children[0].innerHTML=price * num;
        console.log(total);
        alla += total;

    }
    //console.log(allnum);
    all.innerHTML=alla.toFixed(2);

}
s();
//只要数量的input内容发生改变，小计和总价就会更新
let num_all=document.querySelectorAll('#table .num');
for (let j=0;j<num_all.length;j++){
    num_all[j].addEventListener('change',s);
}
//删除操作之后，再根据小计计算总价
let del_all=document.querySelectorAll('#table .del');
for(let k=0;k<del_all.length;k++){
    del_all[k].addEventListener('click',function(){
        this.parentNode.parentNode.parentNode.removeChild(this.parentNode.parentNode);
        s()
    })
}